Field
Embodiments of the present disclosure generally relate to apparatuses and methods for plasma processing of substrates for the deposition and etching of film layers thereon, and for implantation or surface modification thereof using a plasma material flux.
Description of the Related Art
A plasma processing device generates plasma in a process chamber, which plasma is useful for performing various operations upon a workpiece disposed within the process chamber. The different operations may include etching, deposition, and/or ion implantation and surface modification processes. These processes may contribute to the fabrication of three-dimensional structures on the workpiece which may form, for example, discrete devices and/or the electrical interconnection circuitry for a device. Examples of three-dimensional structures which may be formed using these plasma processes include trench capacitors and vertical channel transistors, such as FinFETs.
As performance requirements and feature size shrink for semiconductor devices become more challenging, the types of three dimensional structures used in fabricating integrated circuits have generally become more complex and the dimensions of these structures have decreased. When using a plasma to etch, ion implant, and/or perform deposition processes, an ion flux from the plasma is accelerated toward the workpiece on which the semiconductor device is being formed. In conventional plasma processing where the ions are accelerated to the workpiece via a sheath existing between the plasma and the workpiece, the workpiece surface exposed to the ion flux is inherently orientated orthogonal or substantially orthogonal to the trajectory of the ion flux. This orthogonal trajectory may be useful to create, by etching, trenches, vias, contacts and isolation structures into the exposed surface of the substrate, or by depositing material into recessed features of the substrate. However, as the aspect ratios of substrate features extending thereinto or therefrom become larger, the profile of the sidewall of the feature may become difficult to control. For example, during reactive ion etching of a deep trench feature, sputter etching of the trench bottom or base is achieved by the directional flux of ions drawn to the substrate surface across the sheath, and hence into the trench, generally perpendicular to the substrate surface. However, the products of sputter etching of the bottom of the feature will often deposit on the sidewall of the feature where the directional ion flux does not easily reach.
Controlling the wall profile of a feature and the re-deposition of sputter etched materials thereon can be accomplished by changing the angular trajectory of the ion flux with respect to the workpiece, and thus sputter etch the redeposited material away and/or directly sputter etch the sidewall with energetic ions. However, the angular trajectory of the ion flux has been difficult to control with precision as conventional methods to control the angular trajectory have been difficult to implement. New approaches are needed to control the trajectory of the ion flux.